Slipper



FIG. 1 is a right side elevated view of a slipper showing my new design;

FIG. 2 is a left side elevated view thereof;

FIG. 3 is a rear elevated view thereof;

FIG. 4 is a front plan view thereof; and,

FIG. 5 is a top plan view thereof.

The broken lines illustrate environmental structure and form no part of the claimed design. 

The ornamental design for a slipper, as shown and described. 